Ultrasound Evaluation of Diaphragmatic and Intercostal Muscle Function as an Indicator of COPD Severity: A...

Chronic obstructive pulmonary disease (COPD) is frequently accompanied by respiratory muscle dysfunction, particularly involving the diaphragm and intercostal muscles. This may limit the feasibility of traditional pulmonary function testing.

To investigate the association between ultrasound-derived respiratory muscle parameters and COPD severity, and to evaluate the utility of respiratory muscle ultrasound for disease stratification.

This single-center, prospective study was conducted at Zhejiang Hospital between January 2024 and June 2025, 78 COPD patients (35 mild-to-moderate, 43 severe) and 50 healthy volunteers were enrolled. Muscle thickness, thickening fraction, excursion, and shear-wave elasticity of the diaphragm and intercostal muscles were measured. Group comparisons and logistic regression analyses were performed. Repeatability was evaluated in the healthy cohort.

All 128 participants completed the study. Ultrasound measurements demonstrated excellent repeatability (ICC coefficients 0.851-0.969). Gender (male vs female, OR = 4.934, P = 0.014), DE (OR=0.393, P=0.008), ICMTF (OR=10.053, P=0.025), and ICM-SWV (OR=6.419, P<0.001) were predictive of screening-positive COPD, with an area under the curve (AUC) of 0.908. Within COPD severity stratification, end-inspiratory diaphragmatic thickness (OR=0.041, P=0.014), diaphragmatic thickening fraction (DTF; OR=0.188, P=0.027), and ICM-SWV (OR=5.662, P=0.024) were identified as independent predictors, with an AUC of 0.959.

Respiratory muscle ultrasound offers reproducible and clinically informative parameters that support both COPD diagnosis and severity assessment, providing a potential complementary tool to pulmonary function testing in clinical practice.